How to get credit card in UK

Hi! So I'm 28yrs old and never had a credit card or loan. Just overdraft.

I really want to start working on my credit score and in order to do that I need credit card.

I'm self employed, making around 25k annually, currently about 2k GBP on my account (I get off from overdraft a few months ago though) .

I was denied at my bank TSB and also denied at amazon.

I would be super grateful for advice how to get credit card ASAP. I'm ready to pay deposit or whatever I can do, but TSB doesn't allow that. I'm desperate to get mortgage before I hit 30yrs old so I need to get credit card ASAP.

Any advice please?